This is a really simple (i.e. probably even the most basic possible) example of using the built in aggregate() function in R, basically a sumif in R. Given a set of data where column a is the values and column b contains the data by which you wish to group (in this example categorical data with values of a or b): > data a b 1 0 a 2 0 a 3 1 b 4 2 a 5 2 b 6 2 a 7 3 b 8 4 b 9 7 b The aggregate function as I have used it below takes the following arguments — data$a is the Read more […]